A typical vehicle air bag assembly comprises a container, an inflatable air bag disposed in the container, and an inflator in proximity, to the inflatable air bag. The inflatable air bag is commonly formed of flexible fabric material such as nylon, and is generally stored in the container in a collapsed, folded condition. The air bag has a fluid inlet opening through which fluid (e.g., gas) under pressure can be directed into the air bag. The perimeter of the fluid inlet opening (often referred to as the "mouth" of the air bag) is attached to the container and/or the inflator.
At the onset of a collision, the inflator is actuated and rapidly directs an inert, non-toxic gas (e.g., nitrogen) into the fluid inlet opening in the air bag. The gas forces the air bag out of the container and rapidly inflates the air bag to a predetermined configuration. When inflated to its predetermined configuration, the air bag cushions a vehicle occupant against impact with a structural part of the vehicle.
A known type of vehicle air bag structure essentially comprises a "bag-within-a-bag." An inflatable outer bag is designed to be inflated to a predetermined three dimensional configuration and has an occupant impact area which engages a vehicle occupant who is being pitched toward a structural part of the vehicle by the force of a collision. An inner bag is disposed within the outer bag. The inner bag receives fluid from the inflator and directs the fluid into the outer bag in a predetermined manner, to inflate the outer bag to its predetermined configuration.
For example, in U.S. Pat. No. 3,473,824, fluid is directed into an inner bag. When the pressure in the inner bag reaches a predetermined level, the forward end of the inner bag bursts to allow the fluid to flow forwardly into an outer bag. The inner bag absorbs the kinetic energy of the initial flow of fluid and thereby reduces the possibility that the outer bag will strike an occupant of the vehicle too forcefully. In U.S. Pat. No. 3,900,210, an inflating gas is initially directed into an expandable, elastic inner bag which is contained within an outer bag. As the inner bag expands fluid is directed through apertures in the inner bag into the outer bag in a "forward" direction, i.e., toward the occupant impact area of the outer bag. In a somewhat similar construction, shown in U.S. Pat. No. 3,814,458, an expansible inner bag is not provided with any apertures. Instead, the inner bag expands to conform to the dimensions of the larger outer bag. The expansion of the inner bag dissipates the energy of the inflating gas and physically expands the outer bag to its predetermined three dimensional configuration.
In addition to air bag structures of the "bag-within-a-bag" type, there are air bag structures in which a fluid deflector is disposed within an air bag and deflects fluid from the inflator in predetermined directions to inflate the air bag. For example, in U.S. Pat. No. 3,836,169, a deflector comprises an impervious parachute canopy coupled to an air bag assembly by a porous mesh. The parachute canopy causes fluid directed through the mouth of the air bag to be redirected within the air bag. The patentee states that the purpose of the canopy parachute is to produce a sound deadening effect for the flow of fluid into the air bag. Another example of a fluid deflector within an air bag is shown in U.S. Pat. No. 4,265,468, wherein the deflector is in the shape of a cylinder which is open at both ends. The fluid flows into the cylinder and is then deflected in transverse directions so as to inflate the air bag.